Burner



Patented- Oct. 30,

UNITED. STATES PATENT OFFICE BURNER ration of Illinois Application February 10, 1932, Serial No. 591,953

Claims.

This invention relates to the many types of laboratory burners characterized by a mixing stack through which fuel and air are passed in proper proportion for combustion at the mouth of the stack, the Bunsen burner being a familiar example.

When gas having acomparatively high B. t. u. value is employed with a burner of the character above mentioned, it is almost impossible to mix a lo sufficient quantity of air with the fuel for stable combustion unless the fuel orifice in the base of the burner is very small. However, to so restrict the fuel orifice results in an insufficient quantity 1' of fuel to produce a fiame of practical size. If

this last difficulty, the flame has a tendency to rise from the mouth of the tube and become unstable.

The difliculty above described is encountered only with gas of high B. t. u. value, that is, gas consisting principally of methane and other paraffin hydro-carbons. Artificial gas does not behave in the same manner because it contains an appreciable quantity of hydrogen which renders it more highly combustible.

The present invention provides a simple means for converting aconventional burner into one that will burn gas of high B. t. u. value with a flame stability-comparable to burners employing artificial gas. Further andother objects and advantages will become apparent as the disclosure proceeds and the description is read in conjunction with the accompanying drawing, in which Fig. ,1 is a plan view of a preferred form of the invention;

Fig. 2 isa bottom view of the burner shown in Fig. 1;

Fig. 3 is a sectional view taken on the line 3--3 of Fig. 1; Fig. 4 illustrates the effect of the tube insert on the character of the flame;

Fig. 5 is a fragmentary perspective view of a modified form of the invention; and

Fig. 6 is a view looking into the mouth of the embodiment shown in Fig. 5.

Although but two forms of the present invention are shown and described, it will be understood that the invention may be embodied in various other forms within the scope of the appended claims.

Referring now to the drawing and particularly Figs. 1 to 4 inclusive, the invention is shown applied to a Bunsen burner having a base 10, upon which a mixing stack or burner tube 11 is suitably mounted. Fuel is admitted to the stack the gas or air pressure is increased to overcome through a horizontal passage 12 in the hose nipple 13 and communicates with the enlarged fuel and air mixing chamber 14 by a short upwardly directed restricted passage 15. The top of the mixing chamber 14 is smoothly tapered at 16 to form 60 a shoulder 17 upon which the tubular stack 11 is adapted to seat. The stack is preferably slit horizontally at 18 and vertically at 19 to provide the necessary resilience for inserting the stack in the bore 20 of the base.

Since gas having a high B. t. u. value requires relatively large quantities of air to be mixed with it to obtain suitable combustion, the mixing chamber 14 is preferably of greater diameter than the stack 11. It is also desirable that the fuel admitted to the stack through the orifice 15 strike the tube at the greatest possible obtuse angle in order that there will be a minimum retardance of velocity. To this end, the passage 15 is made as nearly vertical as possible.

The amount of air admitted to the mixing chamber 14 is controlled by a shutter 21 pivoted by a screw 22 to the base of the burner.

It has already been explained that comparatively high air pressure or fuel pressure, or both, is necessary for producing a sizable flame when the fuel orifice 15 is made sufiiciently small for rich gases. The unstable condition of the flame which necessarily results is overcome in the present instance by interiorly fitting a small piece of hexagonal tubing 23 within the mouth of the burner stwk. The insert divides the mouth of the stack into a hexagonal central portion 24 and a plurality of segmental passages 25, the latter being formed between theexterior surface of the insert and the interior adjoining surface of the stack. Preferably the top of the insert is flush with the top of the stack.

Assuming that the burner is operating on fuel of high B. t. u. value and that suflicient air has been combined with it to produce a combustible mixture, it will be seen that as the mixed fuel and air stream reaches the insert, the central and major portion of the stream will pass through the interior of the insert with slightly increased velocity. A portion of the stream, however, will be conducted through the several segmental passages 25 and because of the relatively large surface areas bounding the passages, the velocity of these small streams will be materially reduced. As a result. the gas streams emerging from the passages 25 will combine easily with the oxygen in the surrounding atmosphere and act as a plurality of pilot flames for the main stream.

To state this function in other words, the central stream, which is being projected from the burner at a comparatively high velocity and would normally produce an unstable flame, is surrounded at the mouth of the tube by a protecting zone of stable combustion brought about by the low velocity of the segmental streams.

The character of the flame produced by a burner embodying the principles of this invention shows clearly what takes place at the mouth of the tube. Referring to Fig. 4, by way of explanation, the inner cone 26 (in full line) and the outer cone 27 represent the usual zones of non-combustion and combustion, respectively, formed in all flames. However, it will be observed that in the present instance, the inner cone 26 tapers rapidly as shown at 28 upon emerging from the tube, as compared with the ordinary cone of noncombustion indicated in dotted lines at 29 which is formed when the insert is not used. It thus becomes apparent that there is greater actual combustion near the mouth of the tube when the insert is used than there would otherwise be, and it is believed that this accounts for the stability of the flame.

It will be distinctly understood, however, that the present invention is not limited to any particular theory of operation, although the character of the flame produced by a burner equipped with the present invention apparently substantiates the theories which have been advanced.

The length of the insert depends upon such factors as the kind of gas employed, fuel and air pressure, size of burner, etc. In the embodiment of the invention shown in Figs. 1 to 4 inclusive in which the burner tube has a diameter of inch and stands approximately three and onehalf inches above the base, a horizontal tube insert one-half inch in length is satisfactory for gas of 800 to 1200 B. t. u. value.

It will be understood that the invention may be embodied in many forms and is not limited to the use of hexagonal tubing. For example, triangular, square, or any polygonal tubing may be used in place of hexagonal tubing, or other means may be adopted to secure the retardance of an external portion of the gas stream. An example of one of the many modifications possible is shown in Figs. 5 and 6 in which a cylindrical stack 30 is formed with a substantially square mouth 31 into which a cylindrical tube insert 32 is driven. By this arrangement, the main stream passes through the interior of the insert, while a portion of the stream is retarded in the circumferential passages 33. Preferably the walls of the mouth 31 are rounded at 34 to enable the retarded gas to more completely surround the main stream.

What I claim, therefore, is:

1. In a laboratory burner of the type including a fuel and air mixing stack, a tube insert interiorly fitted within the top of the stack and having a cross sectional shape different from the adjacent portion of the stack, whereby the periphery of the gas stream passes between the outer wall of the insert and the inner wall of the stack and is thereby retarded without materially reducing the volume of gas flow through the stack.

2. In a device of the class described including a fuel and air mixing stack, a thin walled tubular insert fitted into the upper interior portion of the stack with its upper edge substantially flush with the top of the stack, said insert providing, with the adjacent wall of the stack, a plurality of relatively small straight channels through which a portion of the gas stream must pass with a consequent reduction of velocity, the main stream passing through the tubular insert without obstruction or deflection whereby the total volume of flow through the stack is substantially the same as when the insert is not used.

3. In a device of the class described including a fuel and air mixing stack, a tubular insert fitted into the upper interior portion of the stack with its upper edge substantially flush with the top of the stack, said insert serving to divert a relatively small portion of the gas stream through channels formed between the wall of the stack and the insert to thereby reduce the velocity of said portion and form a protecting combustion area surrounding the main flame at the mouth of the stack, the main portion of the stream passing through the insert without obstruction whereby the total volume of flow through the stack is substantially the same as when the insert is not used.

4. In a device of the class described including a cylindrical fuel and gas stack, a thin walled tubular insert, having three or more sides, fitted into the upper interior portion of the stack, with the edges of the insert engaging the walls of the stack, said insert having substantially uniform cross sectional area throughout its length.

5. In a device of the class described including a cylindrical fuel and gas stack, a thin walled tubular insert, having three or more sides, fitted into the upper interior portion of the stack with the edges of the insert engaging the walls of the stack and providing, in conjunction with the adjacent portion of the stack, relatively small passages offering substantial frictional resistance to the flow of gas, said insert having substantially uniform cross sectional area throughout its length.

G. ROSS ROBERTSON. 

